It was easy. I finally got some vinegar and filled it up and let the kettle sit overnight. Rinsed it and gave it a wipe with a wad of paper towel and the scale and residue from the scale is all gone.
Shoulda done it earlier. The wasted psychic energy, every time I peered in and saw the scale…
I mix half water half vinegar and boil it. Then I don’t need to wait overnight. Also boil a few full kettles of clean water to remove the vinegar taste.